Vision system for vehicle

ABSTRACT

A vision system for a vehicle includes an imaging sensor operable to capture an image data set representative of a scene occurring in the exterior field of view of the imaging sensor. A processor processes the captured image data set via an edge detection algorithm, which is applied to a reduced image data set of the captured image data set to detect edges of objects present exteriorly of the equipped vehicle and within a target zone within the exterior field of view of the imaging sensor. The reduced data set is processed more than other image data of the captured image data set in order to detect objects present exteriorly of the equipped vehicle and within the target zone. The target zone encompasses a geographic area of the exterior scene where an object of interest to the driver of the equipped vehicle is realistically expected to be present.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 12/559,856, filed Sep. 15, 2009, now U.S. Pat. No. 8,289,142,which is a divisional application of U.S. patent application Ser. No.12/329,029, filed Dec. 5, 2008, now U.S. Pat. No. 7,679,498, which is adivisional application of U.S. patent application Ser. No. 11/408,776,filed Apr. 21, 2006, now U.S. Pat. No. 7,463,138, which is a divisionalapplication of U.S. patent application Ser. No. 10/427,051, filed Apr.30, 2003, now U.S. Pat. No. 7,038,577, which claims priority of U.S.provisional applications, Ser. No. 60/433,700, filed Dec. 16, 2002; andSer. No. 60/377,524, filed May 3, 2002, which are all herebyincorporated herein by reference in their entireties.

FIELD OF THE INVENTION

The present invention relates generally to vision or imaging systems forvehicles and is related to object detection systems and, moreparticularly, to imaging systems which are operable to determine if avehicle or object of interest is adjacent to, forward of or rearward ofthe subject vehicle to assist the driver in changing lanes or parkingthe vehicle. The present invention also relates generally to a lanedeparture warning system for a vehicle.

BACKGROUND OF THE INVENTION

Many lane change aid/side object detection/lane departure warningdevices or systems and the like have been proposed which are operable todetect a vehicle or other object that is present next to, ahead of orrearward of the equipped vehicle or in an adjacent lane with respect tothe equipped vehicle. Such systems typically utilize statisticalmethodologies to statistically analyze the images captured by a cameraor sensor at the vehicle to estimate whether a vehicle or other objectis adjacent to the equipped vehicle. Because such systems typically usestatistical methodologies to determine a likelihood or probability thata detected object is a vehicle, and for other reasons, the systems maygenerate false positive detections, where the system indicates that avehicle is adjacent to, forward of or rearward of the subject vehiclewhen there is no vehicle adjacent to, forward of or rearward of thesubject vehicle, or false negative detections, where the system, forexample, indicates that there is no vehicle adjacent to the subjectvehicle when there actually is a vehicle in the adjacent lane.

Such known and proposed systems are operable to statistically analyzesubstantially all of the pixels in a pixelated image as captured by apixelated image capture device or camera. Also, such systems may utilizealgorithmic means, such as flow algorithms or the like, to tracksubstantially each pixel or most portions of the image to determine howsubstantially each pixel or most portions of the image has changed fromone frame to the next. Such frame by frame flow algorithms and systemsmay not be able to track a vehicle which is moving at generally the samespeed as the equipped vehicle, because there may be little or norelative movement between the vehicles and, consequently, little or nochange from one frame to the next. Because the systems may thussubstantially continuously analyze substantially every pixel forsubstantially every frame captured and track such pixels and frames fromone frame to the next, such systems may require expensive processingcontrols and computationally expensive software to continuously handleand process substantially all of the data from substantially all of thepixels in substantially each captured image or frame.

Many automotive lane departure warning (LDW) systems (also known as runoff road warning systems) are being developed and implemented onvehicles today. These systems warn a driver of a vehicle when theirvehicle crosses the road's land markings or when there is a cleartrajectory indicating they will imminently do so. The warnings aretypically not activated if the corresponding turn signal is on, as thisimplies the driver intends to make a lane change maneuver. Additionally,the warning systems may be deactivated below a certain vehicle speed.The driver interface for these systems may be in the form of a visualwarning (such as an indicator light) and/or an audible warning(typically a rumble strip sound). One application warns a driver with anindicator light if the vehicle tire is crossing the lane marker and noother vehicle is detected in the driver's corresponding blind spot;and/or further warns the driver with an audible warning if the vehicleis crossing into the adjacent lane and there is a vehicle detected inthe driver's blind spot.

There is concern that the current systems will be more of a driverannoyance or distraction than will be acceptable by the consumer market.Using the turn signal as the principle means of establishing to thewarning system that the maneuver is intentional does not reflect typicaldriving patterns and, thus, many intended maneuvers will cause awarning. As a driver gets annoyed by warnings during intended maneuvers,the driver will likely begin to ignore the warnings, which may result inan accident when the warning is appropriate.

Therefore, there is a need in the art for an object detection system,such as a blind spot detection system or lane change assist system orlane departure warning system or the like, which overcomes the shortcomings of the prior art.

SUMMARY OF THE PRESENT INVENTION

The present invention is intended to provide an object detection system,such as a blind spot detection system, a lane change assist or aidsystem or device, a lane departure warning system, a side objectdetection system, a reverse park aid system, a forward park aid system,a forward, sideward or rearward collision avoidance system, an adaptivecruise control system, a passive steering system or the like, which isoperable to detect and/or identify a vehicle or other object of interestat the side, front or rear of the vehicle equipped with the objectdetection system. The object detection system of the present invention,such as a lane change assist system, utilizes an edge detectionalgorithm to detect edges of objects in the captured images anddetermines if a vehicle is present in a lane adjacent to the equipped orsubject vehicle in response to various characteristics of the detectededges, such as the size, location, distance, intensity, relative speedand/or the like. The system processes a subset of the image datacaptured which is representative of a target zone or area of interest ofthe scene within the field of view of the imaging system where a vehicleor object of interest is likely to be present. The system processes thedetected edges within the image data subset to determine if theycorrespond with physical characteristics of vehicles and other objectsto determine whether the detected edge or edges is/are part of a vehicleor a significant edge or object at or toward the subject vehicle. Thesystem utilizes various filtering mechanisms, such as algorithmsexecuted in software by a system microprocessor, to substantiallyeliminate or substantially ignore edges or pixels that are not or cannotbe indicative of a vehicle or significant object to reduce theprocessing requirements and to reduce the possibility of false positivesignals.

In accordance with the present invention, portions or subsets of theimage data of the captured image which are representative of areas ofinterest of the exterior scene where a vehicle or object of interest islikely to be present are weighted and utilized more than other portionsor other subsets of the image data of the captured image representativeof other areas of the exterior scene where such a vehicle or object ofinterest is unlikely to be present. Thus, in accordance with the presentinvention, a reduced set or subset of captured image data is processedbased on where geographically vehicles of interest are realisticallyexpected to be in the field of view of the image capture device. Morespecifically, for example, the control may process and weight theportion of the captured image data set that is associated with a lowerportion of the image capture device field of view that is typicallydirected generally toward the road surface. Preferably, less thanapproximately 75% of the image data captured by the multi-pixel cameraarrangement is utilized for object detection, more preferably, less thanapproximately 66% of the image data captured by the multi-pixel cameraarrangement is utilized for object detection, and most preferably, lessthan approximately 50% of the image data captured by the multi-pixelcamera arrangement is utilized for object detection.

It is further envisioned that the control may process or weight imagedata within the reduced set or subset which is indicative of physicalcharacteristics of a vehicle or object of interest more than other imagedata within the reduced set which is not likely indicative of or cannotbe indicative of such a vehicle or object of interest. The control thusmay further reduce the processing requirements within the reduced set orsets of image data of the captured image.

Preferably, a multi-pixel array is utilized, such as a CMOS sensor or aCCD sensor or the like, such as disclosed in commonly assigned U.S. Pat.Nos. 5,550,677; 5,670,935; 5,796,094; and 6,097,023, and U.S. patentapplication, Ser. No. 09/441,341, filed Nov. 16, 1999, now U.S. Pat. No.7,339,149, which are hereby incorporated herein by reference, or such asan extended dynamic range camera, such as the types disclosed in U.S.provisional application, Ser. No. 60/426,239, filed Nov. 14, 2002, whichis hereby incorporated herein by reference. Because a multi-pixel arrayis utilized, the image or portion of the image captured by a particularpixel or set of pixels may be associated with a particular area of theexterior scene and the image data captured by the particular pixel orset of pixels may be processed accordingly.

According to an aspect of the present invention, an object detectionsystem for a vehicle comprises a pixelated imaging array sensor and acontrol. The imaging array sensor is directed generally exteriorly fromthe vehicle to capture an image of a scene occurring exteriorly, such astoward the side, front or rear, of the vehicle. The control comprises anedge detection algorithm and is responsive to an output of the imagingarray sensor in order to detect edges of objects present exteriorly ofthe vehicle. The control is operable to process and weight and utilize areduced image data set or subset representative of a target area of theexterior scene more than other image data representative of other areasof the exterior scene. The target area or zone comprises a subset orportion of the image captured by the imaging array sensor and isrepresentative of a subset or portion of the exterior scene within thefield of view of the imaging array sensor. The control thus processes areduced amount of image data and reduces processing of image data thatis unlikely to indicate a vehicle or other object of interest. Theimaging array sensor may be directed partially downwardly such that anupper portion of the captured image is generally at or along thehorizon.

The control may be operable to process portions of the captured imagerepresentative of a target area of the scene and may reduce processingor reduce utilization of other portions of the captured imagerepresentative of areas outside of the target area and, thus, reduce theprocessing of edges or pixels which detect areas where detected edgesare likely indicative of insignificant objects or which are not orcannot be indicative of a vehicle or significant object. The control isthus operable to process and weight and utilize image data from certaintargeted portions of the captured image more than image data from otherportions which are outside of the targeted portions or the target zoneor area of interest.

The control may determine whether the detected edges within the targetarea are part of a vehicle in an adjacent lane in response to variouscharacteristics of the detected edges which may be indicative of avehicle or a significant object. For example, the control may beoperable to process certain areas or portions or subsets of the capturedimage data or may be operable to process horizontal detected edges andfilter out or substantially ignore vertical detected edges. The controlmay also or otherwise be operable to process detected edges which have aconcentration of the edge or edges in a particular area or zone withinthe captured image. The control thus may determine that one or moredetected edges are part of a vehicle in the adjacent lane in response tothe edges meeting one or more threshold levels. Also, the control mayadjust the minimum or maximum threshold levels in response to variouscharacteristics or driving conditions or road conditions. For example,the control may be operable to process or substantially ignore detectededges in response to at least one of a size, location, intensity,distance, and/or speed of the detected edges relative to the vehicle,and may adjust the minimum or maximum threshold levels or criteria inresponse to a distance between the detected edges and the subjectvehicle, a road curvature, lighting conditions and/or the like.

According to another aspect of the present invention, an imaging systemfor a vehicle comprises an imaging array sensor having a plurality ofphoto-sensing or accumulating or light sensing pixels, and a controlresponsive to the imaging array sensor. The imaging array sensor ispositioned at the vehicle and operable to capture an image of a sceneoccurring exteriorly of the vehicle. The control is operable to processthe captured image, which comprises an image data set representative ofthe exterior scene. The control is operable to apply an edge detectionalgorithm to the image captured by the imaging array sensor to detectedges or objects present exteriorly of the vehicle. The control may beoperable to determine whether the detected edges or objects areindicative of a significant object or object of interest. The control isoperable to process a reduced data set or subset of the image data set,which is representative of a target zone or area of the exterior scene,more than other image data representative of areas of the exterior scenewhich are outside of the target zone. The control thus may process imagedata of the reduced data set or subset, such as by applying an edgedetection algorithm to the reduced data set, and substantially discountor limit processing of the other image data which is outside of thereduced data set or subset of the image or of the target zone of theexterior scene.

The control may be operable to adjust the reduced data set or subset andthe corresponding target zone in response to various thresholdcriterion. The control may be operable to adjust the reduced data set ortarget zone in response to a distance to a detected edge or object. Thecontrol may approximate a distance to a portion of a detected edge orobject in response to a location of the pixel or pixels capturing theportion in the captured image. The pixel location may be determinedrelative to a target pixel which may be directed generally at thehorizon and along the direction of travel of the vehicle. For example,the control may be operable to approximate the distance using sphericaltrigonometry in response to a pixel size, pixel resolution and field ofview of the imaging array sensor. The control may access an informationarray which provides a calculated distance for each pixel within thereduced data set or target zone to approximate the distance to theportion of the detected edge or object.

In order to determine if a detected edge or detected edges is/are partof or indicative of a vehicle, the control may be operable to determineif the detected edge or edges is/are associated with an ellipse orpartial ellipse, since the ellipse or partial ellipse may be indicativeof a tire of a vehicle near the equipped vehicle, such as a vehicle in alane adjacent to the equipped vehicle. The control may also be operableto track one or more of the detected edges between subsequent framescaptured by the imaging array sensor to classify and/or identify theobject or objects associated with the detected edge or edges.

The object detection system or imaging system may comprise a lane changeassist system operable to detect vehicles or objects of interestsidewardly of the vehicle. Optionally, the control may be incommunication with a forward facing imaging system. The forward facingimaging system may communicate at least one of oncoming trafficinformation, leading traffic information and lane marking information tothe control of the lane change assist system to assist the lane changeassist system in readily identifying vehicles at the side of the subjectvehicle or adjusting a reduced data set or an area or zone of interestwithin the captured image. The control may be operable to adjust thereduced data set or target zone in response to the forward facingimaging system.

Optionally, the object detection system or imaging system may comprise aforward facing imaging system, such as a lane departure warning system.The lane departure warning system may provide a warning or alert signalto the driver of the vehicle in response to a detection of the vehicledrifting or leaving its occupied lane.

Optionally, the forward facing imaging system may include or may be incommunication with a passive steering system which is operable to adjusta steering direction of the vehicle in response to a detection by theimaging system of the vehicle drifting or leaving its occupied lane.Optionally, the forward facing imaging system may include or may be incommunication with an adaptive speed control which is operable to adjusta cruise control or speed setting of the vehicle in response to roadconditions or traffic conditions detected by the imaging system.Optionally, the imaging system may be in communication with a remotereceiving device to provide image data to a display system remote fromthe vehicle such that a person remote from the vehicle may receive andview the image data with the remote receiving device to determine thelocation and/or condition of the vehicle or its occupants.

According to another aspect of the present invention, a lane changeassist system for a vehicle comprises an imaging sensor and a control.The imaging sensor is positioned at the vehicle and directed generallysidewardly from the vehicle to capture an image of a scene occurringtoward the side of the vehicle. The control is operable to process theimage captured by the imaging array sensor to detect objects sidewardlyof the vehicle. The captured image comprises an image data setrepresentative of the exterior scene. The control is operable to processa reduced image data set of the image data set more than other imagedata of the image data set. The reduced image data set is representativeof a target zone of the captured image.

The control may be operable to adjust the reduced data set or subset ortarget zone in response to an adjustment input. In one form, theadjustment input comprises an output from an ambient light sensor, aheadlamp control and/or a manual control. The control may be operable toadjust the reduced data set or subset or target zone between a daytimezone and a nighttime zone in response to the output. The control may beoperable to adjust a height input for the imaging array sensor such thatthe daytime zone is generally along the road surface and the nighttimezone is generally at a height of headlamps of vehicles.

In another form, the control may be operable to adjust the reduced dataset or subset or target zone in response to a detection of the vehicletraveling through or along a curved section of road. The adjustmentinput may comprise an output from a forward facing imaging system or adetection by the imaging sensor and control that the vehicle istraveling through a curved section of road, such as by the imagingsensor and control detecting and identifying curved lane markers or thelike along the road surface.

It is further envisioned that many aspects of the present invention aresuitable for use in other vehicle vision or imaging systems, such asother side object detection systems, forward facing vision systems, suchas lane departure warning systems, forward park aid systems or the like,rearward facing vision systems, such as back up aid systems or rearwardpark aid systems or the like, or panoramic vision systems and/or thelike.

The present invention may also or otherwise provide a lane departurewarning system that reduces and may substantially eliminate theprovision of an unwarranted and/or unwanted visual or audible warningsignals to a driver of a vehicle when the driver intends to perform thedriving maneuver.

According to another aspect of the present invention, a lane departurewarning system includes an imaging sensor mounted at a forward portionof a vehicle and operable to capture an image of a scene generallyforwardly of the vehicle, and a control for providing a warning signalto a driver of the vehicle in response to an image captured by theimaging sensor. The control is operable to process the image captured todetect at least one of a lane marking, a road edge, a shoulder edge andanother vehicle or object. The lane departure warning system providesthe warning signal in response to a detected object or marking andfurther in response to the vehicle speed or other parameters whichprovide additional information concerning the likelihood that a warningsignal is necessary.

Therefore, the present invention provides an object detection system orimaging system, such as a lane change assist system or other type ofobject detection or imaging system, which is operable to detect andidentify vehicles or other objects of interest exteriorly, such assidewardly, rearwardly, and/or forwardly of the subject vehicle. Theimaging system may primarily process image data within a reduced dataset or subset of the captured image data, where the reduced data set isrepresentative of a target zone or area of interest within the field ofview of the imaging system, and may adjust the reduced data set or zoneor area in response to various inputs or characteristics, such as roadconditions, lighting or driving conditions and/or characteristics of thedetected edges or objects. The imaging system of the present inventionis operable to detect edges of objects, and particularly horizontaledges of objects, to provide improved recognition or identification ofthe detected objects. The imaging system of the present invention may beoperable to limit processing of or to filter or substantially eliminateor reduce the effect of edges or characteristics which are indicative ofinsignificant objects, thereby reducing the level of processing requiredon the captured images.

The edge detection process or algorithm of the lane change assist systemof the present invention thus may provide for a low cost processingsystem or algorithm, which does not require the statisticalmethodologies and computationally expensive flow algorithms of the priorart systems. Also, the edge detection process may detect edges andobjects even when there is little or no relative movement between thesubject vehicle and the detected edge or object. The present inventionthus may provide a faster processing of the captured images, which maybe performed by a processor having lower processing capabilities thenprocessors required for the prior art systems. The lane change assistsystem may also provide a low cost and fast approximation of alongitudinal and/or lateral and/or total distance between the subjectvehicle and a detected edge or object exteriorly of the vehicle and mayadjust a threshold detection level in response to the approximateddistance.

These and other objects, advantages, purposes and features of thepresent invention will become apparent upon review of the followingspecification in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a vehicle equipped with a lane changeassist system in accordance with the present invention, as the vehicletravels along a section of road;

FIG. 2 is a side elevation of the vehicle of FIG. 1;

FIG. 3 is a schematic of a vehicle equipped with the lane change assistsystem of the present invention as the vehicle travels along a sectionof road;

FIG. 4 is another schematic of the vehicle and depicts how the lanechange assist system of the present invention adapts between daytime andnighttime driving conditions;

FIG. 5 is a perspective view of a vehicle as it may be viewed by acamera or image sensor of the lane change assist system of the presentinvention;

FIG. 6 is a top plan view of a vehicle equipped with the lane changeassist system of the present invention, as the vehicle travels around asharp curve in a section of road;

FIG. 7 is a schematic of a pixelated image as may be captured by acamera or image sensor of a lane change assist system in accordance withthe present invention;

FIG. 8 is a schematic of another pixelated image similar to FIG. 7;

FIG. 9 is a block diagram of a top plan view of a vehicle equipped withthe lane change assist system of the present invention and anothervehicle as they travel along a section of road in adjacent lanes to oneanother;

FIG. 10 is a block diagram of a lane change assist system in accordancewith the present invention;

FIGS. 11A-F are diagrams of a virtual camera and characteristics thereofuseful in calculating a distance from the camera of the lane changeassist system to an object detected in the field of view of the camera;

FIG. 12 is a top plan view of a vehicle driving along a road andincorporating a lane departure warning system of the present invention;and

FIG. 13 is another top plan view of the vehicle driving along a road,with another vehicle in an adjacent lane.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings and the illustrative embodiments depictedtherein, an object detection system or imaging system, such as a lanechange assist or aid system 10, is positioned at a vehicle 12 and isoperable to capture an image of a scene occurring sidewardly andrearwardly at or along one or both sides of vehicle 12 (FIGS. 1-4 and6). Lane change assist system 10 comprises an image capture device orsensor or camera 14 and a control 16 (FIGS. 3, 9 and 10). Camera 14captures an image of the scene occurring toward a respective side of thevehicle 12, and control 16 processes the captured image to determinewhether another vehicle 18 is present at the side of vehicle 12, asdiscussed below. Control 16 may be further operable to activate awarning indicator or display or signal device 17 (FIG. 10) to alert thedriver of vehicle 12 that another vehicle is present at the side ofvehicle 12. The warning or alert signal may be provided to the driver ofvehicle 12 in response to another vehicle being detected at the blindspot area (as shown in FIG. 1) and may only be provided when the driverof vehicle 12 actuates a turn signal toward that side or begins turningthe subject vehicle 12 toward that side to change lanes into the laneoccupied by the other detected vehicle 18.

Camera or imaging sensor 14 of object detection system or lane changeassist system 10 is operable to capture an image of the exterior scenewithin the field of view of the camera. The captured image comprises animage data set, which is representative of the exterior scene, and whichis received by control 16. Control 16 is operable to process image datawithin a reduced data set or subset of the image data set more thanother image data of the image data set to reduce the processingrequirements of the control. The reduced data set or subset or subsetsis/are representative of a target zone or area or areas in the exteriorscene where a vehicle or other object of interest may realistically beexpected to be present within the exterior scene. The control is thusoperable to primarily process the significant or relevant area or areasof the scene more than less relevant areas, and may limit or reduceprocessing of or substantially ignore the image data representative ofsome areas of the exterior scene where it is not likely that a vehicleor other object of interest would be present or where a vehicle cannotbe present.

Camera or imaging sensor 14 may comprise an imaging array sensor, suchas a CMOS sensor or a CCD sensor or the like, such as disclosed incommonly assigned U.S. Pat. Nos. 5,550,677; 5,670,935; 5,796,094; and6,097,023, and U.S. patent application, Ser. No. 09/441,341, filed Nov.16, 1999, now U.S. Pat. No. 7,339,149, which are hereby incorporatedherein by reference, or an extended dynamic range camera, such as thetypes disclosed in U.S. provisional application, Ser. No. 60/426,239,filed Nov. 14, 2002, which is hereby incorporated herein by reference.The imaging sensor 14 may be implemented and operated in connection withother vehicular systems as well, or may be operable utilizing theprinciples of such other vehicular systems, such as a vehicle headlampcontrol system, such as the type disclosed in U.S. Pat. No. 5,796,094,which is hereby incorporated herein by reference, a rain sensor, such asthe types disclosed in commonly assigned U.S. Pat. Nos. 6,353,392;6,313,454; and/or 6,320,176, which are hereby incorporated herein byreference, a vehicle vision system, such as a forwardly or sidewardly orrearwardly directed vehicle vision system utilizing the principlesdisclosed in U.S. Pat. Nos. 5,550,677; 5,670,935; and 6,201,642, and/orin U.S. patent application, Ser. No. 09/199,907, filed Nov. 25, 1998,now U.S. Pat. No. 6,717,610, which are hereby incorporated herein byreference, a traffic sign recognition system, a system for determining adistance to a leading vehicle or object, such as utilizing theprinciples disclosed in U.S. Pat. No. 6,396,397, which is herebyincorporated herein by reference, and/or the like.

Camera 14 preferably comprises a pixelated imaging array sensor whichhas a plurality of photon accumulating light sensors or pixels 14 a. Thecamera includes circuitry which is operable to individually access eachphotosensor pixel or element of the array of photosensor pixels and toprovide an output or image data set associated with the individualsignals to the control 16, such as via an analog to digital converter(not shown). As camera 14 receives light from objects and/or lightsources in the target scene, the control 16 may then be operable toprocess the signal from at least some of the pixels to analyze the imagedata of the captured image, as discussed below.

Camera 14 may be positioned along one or both sides of vehicle 12, suchas at or within the exterior rearview mirror 12 a at either or bothsides of vehicle 12. However, camera 14 may be positioned elsewherealong either or both sides and/or at the rear of the vehicle anddirected sidewardly and rearwardly from the vehicle to capture an imageat either side of the vehicle, without affecting the scope of thepresent invention. Camera 14 may be positioned at vehicle 12 andoriented or angled downwardly so as to capture an image which has anupper edge or region generally at the horizon 15, as can be seen withreference to FIGS. 2, 3 and 11C. Positioning or orienting the camera 14in such a manner provides for an increased horizontal pixel count acrossthe captured image at the important areas along the side of vehicle 12,since any vehicle or significant object positioned at or along a side ofthe subject vehicle will be substantially below the horizon and thussubstantially within the captured image. The lane change assist systemof the present invention thus may provide an increased portion of thecaptured image or increased pixel count at important or significant orrelevant areas of the exterior scene, since the area well above the roador horizon is not as significant to the detection of a vehicle at oralong a side of the subject vehicle. Additionally, positioning thecamera to be angled generally downwardly also reduces the adverseeffects that the sun and/or headlamps of other vehicles may have on thecaptured images. Camera 14 thus may be operable to capture substantiallyan entire image of the sideward scene below the horizon.

Control 16 is responsive to camera 14 and processes the signals receivedfrom at least some of the pixels of camera 14 to determine what is inthe captured image. The present invention utilizes physicalcharacteristics of vehicles and roads to reduce or filter out orsubstantially eliminate the signals from some of the pixels and toreduce or eliminate signals or detected images indicative of certaininsignificant or unimportant objects detected within the captured image,as discussed below. For example, control 16 may primarily process theimage data from pixels of camera 14 that are within a reduced data setor subset of the image data of the captured image. The reduced data setof the captured image may be representative of a targeted area or zoneof interest of the exterior scene being captured by the camera. Thetargeted zone may be selected because it encompasses a geographic areaof the exterior scene where a vehicle or other object of interest islikely to be present, while the other image data or areas or portions ofthe captured image may be representative of areas in the exterior scenewhere a vehicle or other object of interest is unlikely to be present orcannot be present, as discussed below. The present invention thus mayprovide for a quicker response time by control 16, since the control 16does not continually process the signals from substantially all of thepixels 14 a of camera 14. Preferably, less than approximately 75% of theimage data captured by the camera is utilized for object detection, morepreferably, less than approximately 66% of the captured image data isutilized for object detection, and most preferably, less thanapproximately 50% of the captured image data is utilized for objectdetection.

Control 16 may include a microprocessor having an edge detectionalgorithm or function 16 a (FIG. 10) which is operable to process or isapplied to the image data received from the individual pixels todetermine whether the image captured by the pixels defines an edge oredges of a significant object, such as an edge or edges associated withor indicative of a bumper 18 a of a vehicle 18 or the like. The edgedetection function or algorithm 16 a of control 16 allows lane changeassist system 10 to interrogate complex patterns in the captured imageand separate out particular patterns or edges which may be indicative ofa vehicle in the adjacent lane, and to substantially ignore or limitprocessing of other edges or patterns which are not or cannot beindicative of a vehicle and thus are insignificant to lane change assistsystem 10. Other information or image data in the captured image orframe which is not associated with edges or which is not associated withsignificant edges (e.g. edges indicative of a portion of a vehicle), maythen be substantially ignored or filtered out by control 16 via variousfiltering processes or mechanisms discussed below to reduce theinformation or image data being processed by control 16 and to reducethe possibility of a false positive detection by control 16. The edgedetection function or algorithm 16 a may comprise a Sobel gradient edgedetection algorithm or other edge detection algorithms commerciallyavailable, and such as disclosed in U.S. Pat. Nos. 6,353,392 and6,313,454, which are hereby incorporated herein by reference.

Control 16 may be operable to determine which edges detected arehorizontal or generally horizontal edges and to limit processing of orto partially filter out or substantially ignore vertical edges. This maybe preferred, since many edges in a vehicle in an adjacent lane will behorizontal or parallel to the road surface, such as edges associatedwith bumper lines, grills, fenders, and/or the like. Control 16 may thusreject or substantially ignore edges which are non-horizontal, therebyreducing the data to be processed. The edge detection algorithm 16 a mayalso provide digital polarization of the captured images to determinehorizontal gradients and to substantially ignore the effects of verticalgradients of the detected edges. For example, the edge detectionalgorithm may use a convolution matrix (such as a one by three matrix orother small matrix or array) which may be processed or applied to theimage data in a single pass across the data received from the pixels 14a of the camera 14 to provide horizontally polarized edge detectionthrough the captured image or a portion thereof. Such horizontalpolarization greatly reduces the possibility that road signs and/orguardrails and/or the like will be processed and analyzed by the controlof the lane change assist system of the present invention, therebyreducing the processing requirements and reducing the possibility of afalse positive signal by the control.

Additionally, the edge detection algorithm 16 a of control 16 mayfunction to detect and determine if there is more than one vehiclepresent at the side of the subject vehicle 12. For example, control 16may distinguish between edges constituting the fronts of differentvehicles and edges constituting the front and side of the same vehicle,since the vehicle fronts typically will have more horizontal edges thanthe vehicle sides.

In order to further reduce the processing requirements and thepossibility of a false positive indication, and thus enhance theresponse time and system performance, control 16 may process signals orimage data from pixels that are oriented or targeted or arranged orselected to capture images of objects or items that are at leastpartially positioned within a predetermined or targeted area or zone ofinterest. The zone of interest may be defined by an area or region atthe side of the subject vehicle where another vehicle or significantobject may be positioned, such as in the blind spot region of that sideof the vehicle, which would be significant or important to lane changeassist system 10. For example, the zone of interest or “polygon ofinterest” may be directed rearward from the camera and toward or aroundthe center of the adjacent lane. By substantially isolating the zone ofinterest, or substantially filtering out or substantially ignoring orreducing utilization of edges or signals or image data of the capturedimage which are representative of areas outside of the zone or area ofinterest, the system of the present invention may reduce the image dataor information to be processed by control 16 and may substantiallyreduce the possibility that a false positive signal will occur. Forexample, if an object is detected substantially to one side or the otheror substantially at the bottom of the captured image, such an object isnot likely to be a vehicle positioned within the blind spot area of thesubject vehicle 12, whereby control 16 may reduce processing of or maynot process image data from the pixels capturing that area of the sceneor may substantially ignore such a detected edge or object in subsequentprocessing of the image data captured by the pixels 14 a of camera 14.

It is further envisioned that control 16 may process the image data ofpixels capturing images representative of an area within the zone ofinterest and may not indicate a positive signal of a vehicle or othersignificant object in the adjacent lane unless a detected edge withinthe reduced image data set or subset or zone of interest is greater thana minimum size threshold, or spans a threshold number of pixels.Optionally, control 16 may require that a detected edge span or includea threshold number of pixels that are within a predetermined “hot zone”or specific targeted area within the zone of interest before the edgewill be considered significant for further processing. The targeted zoneor hot zone may be defined as a reduced zone or area near the center ofthe zone of interest or targeted road space or adjacent lane. Thecontrol 16 thus may require a substantial portion of the detected edgeor edges to be within the smaller hot zone before the control mayconsider the edges to constitute a portion of a vehicle in the adjacentlane or other significant object. This also may substantially reduce theprocessing requirements and may substantially reduce the possibility ofa false positive signal being generated by control 16.

The reduced image data set of the captured image which is representativeof the zone of interest of the exterior scene may be adjusted by control16 in response to various road or driving conditions, lightingconditions, and/or characteristics of the detected edges or objects. Thereduced data set or zone of interest thus may be adaptable to variousconditions encountered by the vehicle, such that the control may furtherreduce the processing requirements and enhance the efficiency of thesystem by primarily processing image data from some pixels and ignoringimage data from other pixels depending on the present conditionssurrounding the vehicle.

For example, as shown in FIG. 4, control 16 may be operable to adjust oradapt the image data subset or zone or area of interest between daytimeand nighttime driving conditions. During daytime driving conditions,detecting the edge of the front horizontal shadow 18 b (FIG. 4) of avehicle 18 or the bumper 18 b of a vehicle 18 may be the method forsignificant object or vehicle detection by the lane change assist systemof the present invention. However, during nighttime driving conditions,where such vehicle characteristics may not be visible to the camera 14,the primary detection characteristic may be the headlights 18 c of avehicle 18 approaching from the rear of the subject vehicle. Control 16may thus adjust or adapt the reduced data set or target zone in responseto an output or signal from an ambient light sensor (which detects theambient light intensity present at or around the subject vehicle), aheadlamp control, a headlamp switch, a manual control or input and/orthe like (shown generally at 20 in FIG. 10). More particularly, thereduced data set or zone of interest may be raised to correspond to thetypical height or range of height of a headlight of a typical vehicle,so that control 16 may primarily process image data from pixels whichreceive light from headlamps of vehicles in the adjacent lane.

As shown in FIG. 4, the adjustment of the reduced data set or zone maybe adjusted mathematically by changing the height (γ, γ′) of the cameraas input to the control (such as between a daytime camera height showngenerally at y and a nighttime camera height shown generally at γ′),such that all of the geometry of the zone of interest is adjustedupward. Because headlights of vehicles are generally within a certaindistance or range above the road surface, the control may be operable toadjust the reduced data set or zone of interest to adapt to thisgeometric change in the detection characteristic. A daytime perspectivetriangle associated with the camera is shown generally at D in FIG. 4,while a nighttime perspective triangle associated with the camera isshown generally at N in FIG. 4.

It is further envisioned that the reduced data set or area or zone ofinterest may be changed or adapted to accommodate sharp curves in theroad that the subject vehicle 12 is traveling through or has traveledthrough. In situations where a vehicle travels along a sharp curve inthe road, a lane change assist system may consider a guardrail orvehicle 18′ in another lane to be a vehicle or object of interest in theadjacent lane, since the other vehicle or object may be positionedgenerally at or near the zone of interest of the lane change assistsystem, as can be seen in FIG. 6. Control 16 may be operable to processthe image data or signals from the pixels 14 a of camera 14 to determinelane markers along the road, or a shoulder of the road or the like, inorder to determine the road curvature as the vehicle 12 travels alongthe section of road. In situations where a sharp curve in the road isdetected, control 16 may be operable to alter or reshape the reduceddata set or area or zone of interest and/or to adjust the distancethresholds (discussed below) or to adjust other filteringcharacteristics or criteria or thresholds to accommodate such a curve inthe road. The lane change assist system of the present invention thusmay use road curvature information to adjust how far back and/or wherethe camera and/or control may look for significant objects or vehicles.The lane change assist system thus substantially avoids providing afalse positive signal upon detection of another vehicle 18′ or guardrailor the like which is not in the adjacent lane, since such a vehicle orobject may not be within the adjusted zone of interest of the lanechange assist system.

Optionally, control 16 may be further operable to substantiallyeliminate or substantially ignore image data representative of objectsor edges which are too large or too small to be considered part of avehicle in the adjacent lane. If a detected edge is too small, such asif the horizontal pixel span or vertical pixel span is very small, thecontrol may reduce processing of the edge or the edge may be removedfrom further processing, since it does not represent a significant edgeto the lane change assist system 10. Likewise, if an edge is too large,the control may reduce processing of the edge or it may also be removedfrom further processing since it does not represent a vehicle in theadjacent lane. The threshold size of the detected edge or object mayalso vary in response to the distance to the edge or object, asdiscussed below.

Additionally, lane change assist system 10 may be operable to determinewhether a detected edge or object is a vehicle in an adjacent lane inresponse to one or more other detection thresholds or criteria. Further,control 16 may be operable to vary one or more detection thresholds orcriteria at which a detected edge or object is considered a vehicle orsignificant object. The threshold values may thus be variable and may beadjusted in response to driving conditions, road curvature, location ofthe detected edges and/or the distance between the camera and thedetected object and/or the like. For example, the threshold value orvalues may be adjusted in response to the distance so that control 16more readily accepts and processes detected edges as the object they arerepresentative of gets closer to or approaches the subject vehicle.

For example, control 16 may have a minimum gradient threshold at whichcontrol 16 determines whether or not a detected edge is to be includedin further processing of the captured image. Control 16 thus may beoperable to determine the vertical and/or horizontal gradient of thedetected edges and may substantially eliminate or filter out edges witha gradient below a threshold gradient level, since such edges cannot berepresentative of a vehicle or object which is significant to the lanechange assist system. The control thus may further substantiallypreclude false positive signals and reduce further processing of thepixel signals.

However, as an object or other vehicle approaches the subject vehicle12, the detected edge or edges representative of the object tends toresolve or reduces and spreads out the gradient across multiple pixels,thereby reducing the gradient at a particular pixel. Control 16 thus maybe further operable to adjust the minimum gradient threshold in responseto the distance to the detected object. By using a calculated orestimated or approximated distance to the detected object or a table ofperspective calculations or distance approximations, discussed below,the minimum gradient threshold may be reduced proportionally in responseto the estimated or tabulated distance data to provide enhanced edgedetection at closer ranges.

By detecting edges of objects within the reduced data set or zone orarea of interest (and adjusting the zone of interest for particulardriving conditions or situations), and by focusing on or concentratingon or primarily processing the horizontal edges detected or other edgeswhich may be indicative of a vehicle or significant object, whilesubstantially filtering out or substantially ignoring other image dataor edges or information, the present invention substantially reduces thepossibility of false positive signals. In order to further reduce thepossibility of such false positive signals, control 16 may be operableto determine a distance between a detected object and the subjectvehicle to further filter out or substantially eliminate objects thatare not within a predetermined range or threshold distance from thesubject vehicle and which, thus, may be insignificant to the lane changeassist system of the present invention.

In a preferred embodiment, camera 14 and control 16 may be operable toapproximate the distance to an object or vehicle in response to a pixelcount of the number of pixels between the pixels capturing the object(or an edge of the object) and the pixels along an edge of the camera ordirected toward and along the horizon of the captured image. Moreparticularly, with the camera 14 oriented with the video framehorizontal scan lines or pixels being generally parallel to the horizon,perspective calculations may be made to provide a table of entries ofparticular distances which correspond to particular horizontal lines orpixels in the video frame which may detect or sense a forward edge of anadjacent vehicle at the ground level, such as an edge corresponding to ashadow of the front of the vehicle 18 or an edge corresponding to theintersection of the tire 18 d of the vehicle 18 on the road surface orthe like. The distance to an object captured by an edge detected in thecaptured image may then be approximated by determining a vertical pixelcount and retrieving the appropriate distance entry corresponding tothat particular horizontal line or pixel count or position. The presentinvention thus provides for a quick and inexpensive means fordetermining or estimating or approximating the distance between thesubject vehicle and an object or edge detected in the area or zone ofinterest by determining a horizontal line count from the horizon down tothe pixels capturing the detected edge.

As can be seen with reference to FIGS. 3 and 7-9 and as discussed below,the location and distance of a closest point φ on a detected edge orobject relative to camera 14 or subject vehicle 12 may be calculatedbased on known or assigned parameters of the location of camera 14 and ahorizontal and vertical pixel count between a target or alignment point14 b (FIGS. 7 and 8) and the closest point φ. This may be accomplishedbecause the lowest detected edge of a vehicle may be considered to beindicative of a forward shadow of the front bumper of the vehicle on theroad surface or may be indicative of the intersection of the tire andthe road surface. Because such edges are generally at or near the roadsurface, the distance to the detected object may be calculated usingknown geometrical equations given the height of the camera on thesubject vehicle (as input to the control). Control 16 thus may quicklydetermine the distance to a detected object and may be easily calibratedfor different applications of the lane change assist system. Thecalculated distances corresponding to at least some of the pixels 14 aof camera 14 may be entered into a table or database, such that control16 may be operable to quickly obtain an estimated distance between thecamera and the closest point of a detected edge or object once at leastthe vertical pixel count between the closest point φ and the horizon ortarget or alignment point 14 b is determined.

More particularly, in order to determine the total distance betweencamera 14 and the closest point of a detected edge or object, thelateral distance ψ and longitudinal distance δ may be calculated andused to obtain the total distance τ. Because the lateral distance ψshould be approximately constant for an edge or vehicle detected in thezone or area corresponding to the adjacent lane, the lane change assistsystem 10 may only calculate or tabulate and access the longitudinaldistance δ for the detected edges, whereby the distances may becalculated and tabulated for each horizontal line count down from thehorizon or target point. More particularly, the longitudinal distance δmay be calculated or approximated by determining a pixel count(Pixels_(β)) downward from the horizon 15 to the detected edge or pointφ. The pixel count may be used to obtain a value for the downward angleβ (FIG. 3) between camera 14 and the detected object, which is derivedfrom the following equation (1):

β=Pixels_(β) *v;   (1)

where v is the vertical view angle per pixel of the camera and isobtained via the following equation (2):

v=(Optical Field Height Degrees)/(Vertical Pixel Resolution);   (2)

where the Optical Field Height Degrees is the vertical angle of view ofthe camera and the Vertical Pixel Resolution is the number of horizontalrows of pixels of the camera. The downward angle β is then calculated todetermine the angle between the horizon and the forward edge of thedetected object at the ground. The longitudinal distance δ between thevehicles may then be determined or approximated by the followingequation (3):

δ=γ*tan(90°−β);   (3)

where γ is the height of the camera 14 above the ground as input to thecontrol 16, and as best shown with reference to FIG. 3. As discussedabove, the height input to control 16 may be adjusted between γ and γ′(FIG. 4) to adjust the zone of interest for daytime versus nighttimedriving conditions. Such an adjustment also adjusts the distancecalculations to determine the distance to the detected headlamps, whichare above the ground or road surface.

Likewise, if desired, the lateral or sideward location or distance ψ tothe closest point φ on the detected edge or object may be calculated byobtaining a horizontal pixel count Pixel_(βmin), such as by counting ordetermining the pixels or pixel columns from the alignment point 14 bhorizontally across the captured image to the pixel column correspondingto the closest point φ. This pixel count value may be used to calculatethe lateral distance to the detected edge or object, which may in turnbe used to calculate or estimate the total distance to the detectedobject. More particularly, the lateral angle ω (FIG. 9) between camera14 at the side of vehicle 12 and the detected object may be determinedby the following equation (4):

ω=Pixel_(βmin)*λ;   (4)

where λ is the horizontal view angle per pixel of the camera and isobtained via the following equation (5):

λ=Optical Field Width Degrees/Horizontal Pixel Resolution;   (5)

where the Optical Field Width Degrees of camera 14 is the angle of viewof the camera and the Horizontal Pixel Resolution is the number ofcolumns of pixels of camera 14.

Optionally, the lateral angle ω (FIG. 9) between camera 14 at the sideof vehicle 12 and the detected object may be determined using sphericaltrigonometry, which may provide a more accurate lateral angle ωdetermination than equations 4 and 5 above. Using sphericaltrigonometry, discussed below, or the equations set forth above, a table(image space) of horizontal angles may be produced at initialization orstartup of the lane change assist system 10 to determine the horizontalangle for each pixel position on the captured image. Because thehorizontal angle is not independent of the vertical angle, an imagespace may be created and the horizontal view angle of every pixel may bestored therein. An example of such an image space or array is depictedin FIG. 11F.

In determining the perspective geometry, the parameters of a virtualcamera 14′ are determined or assigned and implemented (see FIGS.11A-11E). The virtual camera 14′ does not actually exist, butcalculations may be made to determine an effective focal length (inpixels) of the virtual camera. To work with the perspective geometry,spherical trigonometry may be employed to determine where each pixel onthe camera is directed toward. In spherical trigonometry, lateral anglesmay be calculated based on both horizontal and vertical pixel positionsof the detected edge grouping or point. The relationship betweenhorizontal angles and vertical angles may be used to calculate orgenerate a table of horizontal angles and/or distances to an edge orobject detected by each pixel.

The virtual camera geometry may be calculated and used to determine therelationship between each pixel of the captured image and the locationon the road surface that the pixel corresponds to. These calculationsmay be based on an assumption that lines perpendicular to the directionof travel of the subject vehicle may be on a plane which is generallyparallel to the horizon and, thus, parallel to the image or pixel linesor rows, since the camera is positioned or oriented such that thehorizontal rows of pixels are generally parallel to the horizon. Thisallows the control to determine the distance along the vehicle forwarddirection in response to the row of pixels on which the object has beendetected, assuming that the camera is detecting an edge of the detectedobject or other vehicle (such as the front shadow edges, tires or thelike) along the pavement or road surface.

An array of pixels 14 a′ and a focal length (in pixels) vfl of thevirtual camera 14′ is shown in FIGS. 11A, 11B and 11E. The virtual focallength vfl at the frame center of the virtual camera 14′ may bedetermined by the following equation (6):

vfl=(Pixel Resolution/2)/(tan(Frame Angular Size/2));   (6)

where the Frame Angular Size is the angular field of view of the camera14. This equation may be used to calculate the virtual focal length ofan imaginary pinhole camera with an infinitely small pinhole lens invertical pixels vvfl and the virtual focal length in horizontal pixelshvfl using the pixel resolutions and frame angular sizes in the verticaland horizontal directions, respectively. The virtual focal length iscalculated in both vertical pixel units and horizontal pixel unitsbecause the vertical and horizontal sizes of the pixels may be differentand the camera may have a different pixel resolution and frame angularsize or field of view between the vertical and horizontal directions.

The vertical or downward view angle β to the object may be determined bythe following equation (7):

β=arc tan(Vertical Pixels)/(vvfl);   (7)

where Vertical Pixels is the number of pixels or rows of pixels downfrom the target row or horizon. The view angle thus may be calculatedfor any line of pixels according to equation (7). An array for each ofthe view angle values may be calculated and stored for rapid distancecalculations. The downward angle β may then be used to calculate thelongitudinal distance δ in a similar manner as discussed above. Asdiscussed above, the longitudinal distance calculations assume that fora detected edge or object along a row of pixels, the longitudinaldistance to the edge or object is the same for any pixel along the row,since the camera is oriented with the rows of pixels being generallyparallel to the horizon and generally perpendicular to the direction oftravel of the vehicle.

In order to determine the location and angle and distance to a detectedobject or edge (which may be represented by a point along an object,such as at coordinate x, y of the pixel array (FIG. 11A)), the effectivefocal length of the virtual camera for the point on the detected objectmay be calculated. As shown in FIG. 11E, the effective focal length invertical pixels (vefl) may be calculated by the following equation (8):

vefl=(vvfl ²+(y−height/2)²)^(1/2);   (8)

where height/2 is one-half of the vertical image height (in pixels) ofthe camera. The effective focal length in horizontal pixels (hefl) maythen be calculated by converting the effective focal length in verticalpixel units to horizontal pixel units via the following equation (9):

hefl=hvfl*vefl/vvfl.   (9)

The horizontal angle ω to the detected point in the image may becalculated via the following equation (10):

ω=arc tan(Horizontal Pixels/hefl);   (10)

where Horizontal Pixels is the number of columns of pixels (orhorizontal distance in pixels) that the point x, y is from the target oralignment or aft point or pixel. The Horizontal Pixels value may becounted or calculated by the control. The calculations for theHorizontal Pixels value may be different for the opposite sides of thevehicle in applications where the zero coordinate of the pixel array maybe on the vehicle side of the array for a camera on one side of thevehicle, such as on the passenger side of the vehicle, and may be on theoutside of the array for a camera on the other side of the vehicle, suchas on the driver side of the vehicle. In the illustrated embodiment ofFIG. 11A, the Horizontal Pixels may be calculated by subtracting thex-coordinate for the aft pixel or alignment point 14 b′ from thex-coordinate of the detected point x, y.

Such calculations may provide a more precise and true value for thelateral angle ω between the camera 14 and the detected object. Thelateral distance ψ to the detected object may thus be calculated by thefollowing equation (11):

ψ=δ*tan(ω).   (11)

Accordingly, the actual distance τ between camera 14 and the closestpoint on the detected object may be obtained by the following equation(12):

τ=(δ²+ψ²)^(1/2).   (12)

Because the lateral, longitudinal and total distances are calculatedusing certain known or obtainable characteristics and geometricalrelationships, such as the input height of camera 14 above the ground,the pixel resolution of camera 14, the field of view of the camera, anda pixel count in the horizontal and vertical direction with respect to atarget point or alignment target and/or the horizon, the calculateddistance and/or angle values for each pixel count or location may beentered into a table to provide a rapid response time for determiningthe distance to the detected edge or object once the pixel count orlocation of the detected edge is known.

As discussed above, the lane change assist system may only be concernedwith the longitudinal distance δ to the detected edge. Control 16 maythus determine a vertical pixel count and approximate the longitudinaldistance to the detected object or edge via equations (1), (2) and (3)or via the data table, thereby significantly reducing the processingrequirements of control 16 to estimate or calculate the distance to thedetected edges or objects.

Additionally, control 16 may be operable to substantially eliminate orsubstantially ignore other forms or types of detected edges which arenot likely or cannot be part of a vehicle in the adjacent lane. Forexample, as can be seen in FIG. 5, the tires and wheels 18 d of anadjacent or approaching vehicle 18 are viewed as ellipses from a forwardand sideward angle with respect to the adjacent vehicle. Because allvehicles on the road have tires, control 16 of lane change assist system10 may be operable to process the signals from the pixels (such as thepixels directed toward the zone of interest) to detect the presence ofone or more ellipses at or near the detected edges. If an ellipse orwheel is not detected, then the detected edges and associated object maybe eliminated from processing by control 16, since it cannot be avehicle in the adjacent lane. Detecting the presence of ellipses andwheels or portions thereof can thus assist in providing informationregarding the existence of a vehicle and may assist in determining theposition and/or velocity or relative position and/or relative velocityof the detected vehicle with respect to vehicle 12.

In order to further reduce the possibility of control 16 generating afalse positive signal, control 16 of lane change assist system 10 may beoperable to determine an intensity or brightness level associated withthe detected edges and to substantially eliminate edges which do notsignificantly change in brightness level or intensity level from oneside of the detected edge to the other. This is preferred, since linesin the road, thin branches on the road and/or many other small articlesor objects may not resolve, and thus may result in single edges that donot significantly change in brightness or intensity (or color if a colorsystem is used) across their detected edges. However, a significantchange in brightness or intensity would be expected along a detectededge of an automotive body panel or bumper or other component orstructure of a vehicle or the like. Accordingly, control 16 maysubstantially eliminate or substantially ignore edges or objects whichdo not have a significant brightness or intensity change thereacross,since an edge with an insignificant change in brightness or colorsignifies an insignificant edge which can be substantially eliminated.By substantially eliminating such insignificant edges, control 16 mayfurther significantly reduce the computational requirements orprocessing requirements, while also significantly reducing thepossibility of a false positive indication.

Control 16 may also be operable to compare image data from consecutiveframes or images captured by camera 14 to confirm that a detected edgeor object is representative of a vehicle in an adjacent lane and/or todetermine the relative speed between the detected object or vehicle andthe equipped or subject vehicle 12. By extracting collections of edgesor points of interest, such as ellipses, bend maximums in edges and/orthe like, from consecutive frames, and correlating such points ofinterest from one frame to the next, the lane change assist system ofthe present invention can more effectively verify the pairing of suchcharacteristics or objects. The control may track or correlate thepoints of interest based on the placement or location of the edgeswithin the captured images, the general direction of travel of thedetected edges or groups of edges between consecutive frames, thedimensions, size and/or aspect ratio of the detected edges or objectsand/or the like. Confirming such characteristics of edges and groups ofedges and objects allows the lane change assist system to track theobjects from one captured frame or image to the next. If the relativespeed or movement of the detected edge or object is not indicative ofthe relative speed or movement of a vehicle in the adjacent lane,control 16 may filter out or substantially ignore such detected edges infurther processing so as to reduce subsequent processing requirementsand to avoid generation of a false positive signal. Lane change assistsystem 10 may also be operable to connect collections of such objects oredges based on relative motion between the subject vehicle and thedetected object or edges. Such connected collections may provideinformation about the size and shape of the detected object for objectclassification and identification by control 16.

It is further envisioned that lane change assist system 10 may beoperable in conjunction with a lane departure warning system or otherforward facing imaging system 22 of vehicle 12, such as a lane departurewarning system of the type discussed below or as disclosed in U.S.provisional application, Ser. No. 60/377,524, filed May 3, 2002, whichis hereby incorporated herein by reference, or any other lane departurewarning system or the like, or a headlamp control system, such asdisclosed in U.S. Pat. No. 5,796,094, which is hereby incorporatedherein by reference, or any forwardly directed vehicle vision system,such as a vision system utilizing principles disclosed in U.S. Pat. Nos.5,550,677; 5,670,935; 6,201,642; and 6,396,397, and/or in U.S. patentapplication, Ser. No. 09/199,907, filed Nov. 25, 1998, now U.S. Pat. No.6,717,610, which are hereby incorporated herein by reference. Theforward facing imaging system may provide an input to lane change assistsystem 10 to further reduce any likelihood of a false positive signalfrom the lane change assist system.

For example, the forward facing imaging system may detect lane markersat the road surface to detect a curvature in the road that the subjectvehicle is approaching and/or traveling along. Such information may becommunicated to lane change assist system 10, so that control 16 mayadapt or shape the reduced image data set or zone of interest as thesubject vehicle 12 enters and proceeds along the detected roadcurvature, as discussed above. Also, the forward facing imaging systemmay detect headlamps of oncoming or approaching vehicles. If the laneforward and to the left of vehicle 12 has oncoming traffic, control 16may substantially ignore the left side of the vehicle, since the lanechange assist system would not be concerned with a lane change intooncoming traffic. Also, the forward facing imaging system may detect thetail lights or rear portion of a leading vehicle in another lane, andmay track the leading vehicle relative to the subject vehicle. As thesubject vehicle overtakes the leading vehicle, the lane change assistsystem may then be alerted as to the presence of the overtaken vehicle,such that edges detected in that lane a short period of time after theovertaken vehicle leaves the range of the forward facing imaging system(the period of time may be calculated based on the relative velocitybetween the subject vehicle and the overtaken vehicle) may be readilyidentified as the now overtaken and passed vehicle. By utilizing thevehicle information of a vehicle detected by a forward facing imagingsystem, the lane change assist system of the present invention (or otherside object detection systems or the like) may reduce the amount ofprocessing of the captured images or detected edges, since such avehicle may be readily identified as the vehicle that was previouslydetected by the forward facing imaging system. This avoids a duplicationof efforts by the forward facing imaging system and lane change assistsystem of the vehicle.

By primarily processing image data and detected edges in certain areasand/or processing image data and detected edges that meet certainthresholds or criteria, and substantially rejecting or substantiallyignoring other information or image data or edges, such as detectededges that are substantially non-horizontal, or other edges that cannotbe part of a vehicle, or image data that are not representative of azone of interest of the exterior scene, the lane change assist system ofthe present invention substantially reduces the image data to beprocessed by control 16. It is envisioned that such a reduction in theamount of image data to be processed may allow the lane change assistsystem to have a control which comprises a micro-processor positioned atthe camera. Accordingly, the lane change assist system may be providedas a module which may be positioned at either or both sides of thevehicle, and which may be connected to an appropriate power source orcontrol or accessory of the vehicle.

Therefore, the present invention provides a lane change assist systemwhich is operable to detect and identify vehicles or other objects ofinterest sidewardly and/or rearwardly of the subject vehicle. The lanechange assist system of the present invention is operable to detectedges of objects, and particularly horizontal edges of objects, toprovide improved recognition or identification of the detected objectsand reduced false positive signals from the lane change assist system.The lane change assist system may primarily process information or imagedata from a reduced set or subset of image data which is representativeof a target zone or area of interest within the exterior scene and mayadjust the reduced data set or target zone in response to driving orroad conditions or the like. The edge detection process or algorithm ofthe lane change assist system of the present invention provides for alow cost processing system or algorithm, which does not require thestatistical methodologies and computationally expensive flow algorithmsof the prior art systems. Also, the edge detection process may detectedges and objects even when there is little or no relative movementbetween the subject vehicle and the detected edge or object.

The lane change assist system of the present invention thus may beoperable to substantially ignore or substantially eliminate or reducethe effect of edges or characteristics which are indicative ofinsignificant objects, thereby reducing the level of processing requiredon the captured images and reducing the possibility of false positivedetections. The lane change assist system may also provide a low costand fast approximation of a longitudinal and/or lateral and/or totaldistance between the subject vehicle and a detected edge or object at aside of the vehicle and may adjust a threshold detection level inresponse to the approximated distance. The lane change assist system ofthe present invention may be operable to substantially ignore certaindetected edges or provide a positive identification signal depending onthe characteristics of the detected object or edge or edges, the drivingor road conditions, and/or the distance from the subject vehicle. Thepresent invention thus may provide a faster processing of the capturedimages, which may be performed by a processor having lower processingcapabilities then processors required for the prior art systems.

Although the present invention is described above as a lane changeassist or aid system or side object detection system, it is envisionedthat many aspects of the imaging system of the present invention aresuitable for use in other vehicle vision or imaging systems, such asother side object detection systems, forward facing vision systems, suchas lane departure warning systems, forward park aids, passive steeringsystems, adaptive cruise control systems or the like, rearward facingvision systems, such as back up aids or park aids or the like, panoramicvision systems and/or the like.

For example, an object detection system or imaging system of the presentinvention may comprise a forward facing lane departure warning system110 (FIG. 1), which may include an image sensor or camera 114 and acontrol 116 positioned on or at vehicle 12. Lane departure warningsystem 110 is generally shown at the front of the vehicle 12 with camera114 positioned and oriented to capture an image of the region generallyforwardly of the vehicle. However, the camera may optionally bepositioned elsewhere at the vehicle, such as within the vehicle cabin,such as at an interior rearview mirror assembly of the vehicle or at anaccessory module or the like, and directed forwardly through thewindshield of the vehicle, without affecting the scope of the presentinvention. Camera 114 is operable to capture an image of a sceneoccurring forwardly of the vehicle and control 116 is operable toprocess image data of the captured images or frames to detect andmonitor or track lane markers or road edges or the like or oncoming orapproaching vehicles or objects, and to provide a warning or alertsignal to a driver of the vehicle in response to the detected images,such as in the manner disclosed in U.S. provisional application, Ser.No. 60/377,524, filed May 3, 2002, which is hereby incorporated hereinby reference.

Similar to camera 14 of lane change assist system 10, discussed above,camera 114 may be positioned at vehicle 12 and oriented generallydownwardly toward the ground to increase the horizontal pixel countacross the captured image at the important areas in front of vehicle 12,since any significant lane marking or road edge or the like, or othervehicle approaching or being approached by the subject vehicle,positioned in front of or toward a side of the subject vehicle will besubstantially below the horizon and thus substantially within thecaptured image. The lane departure warning system of the presentinvention thus may provide an increased portion of the captured image orincreased pixel count at important areas of the exterior scene, sincethe area well above the road or horizon is not as significant to thedetection of lane markers and the like and/or other vehicles.Additionally, positioning the camera to be angled generally downwardlyalso reduces the adverse effects that the sun and/or headlamps of othervehicles may have on the captured images.

Control 116 of lane departure warning system 110 may include an edgedetection algorithm or function, such as described above, which isoperable to process or may be applied to the individual pixels todetermine whether the image captured by the pixels defines an edge oredges of a lane marker or the like. The edge detection function oralgorithm of control 116 allows lane departure warning system 110 tointerrogate complex patterns in the captured image and separate outparticular patterns or edges which may be indicative of a lane marker orthe like, and to substantially ignore other edges or patterns which arenot or cannot be indicative of a lane marker or the like and thus areinsignificant to lane departure warning system 110. Other information inthe captured image or frame, which is not associated with significantedges, may then be substantially ignored or filtered out by control 116via various filtering mechanisms or processing limitations to reduce theinformation being processed by control 116.

Control 116 may be operable to determine which detected edges are angledor diagonal across and along the captured image and to partially filterout or substantially ignore or limit processing of vertical and/orhorizontal edges. This may be preferred, since edges indicative of alane marker may be angled within the captured image, as can be seen withreference to FIGS. 7 and 8. The control may thus process edges which areangled and which move diagonally through the scene from one frame to thenext. Control 116 may be operable to skew or bias the rows of pixels inthe pixelated array to simulate horizontal edges with the angled edges,such that control may detect and track such edges while substantiallyignoring other edges. Control 116 may thus reject or substantiallyignore edges which are not indicative of lane markers or the like (andwhich are not indicative of another vehicle forward of and approachingthe subject vehicle), thereby reducing the data to be processed.

In order to further reduce the processing requirements and thepossibility of a false detection or indication of a lane marker, and toenhance the response time and system performance, control 116 mayprimarily process signals or image data from pixels that are oriented ortargeted or arranged or selected to capture images of objects or markersthat are at least partially positioned within a predetermined ortargeted area or zone of interest of the exterior scene. The zone ofinterest may be defined by an area or region forwardly and toward one orboth sides of the subject vehicle where a lane marker or road side oredge may be positioned, which would be significant or important to lanedeparture warning system 110. By substantially isolating the reduceddata set representative of the zone of interest, or substantiallyfiltering out or substantially ignoring edges or signals or image datawhich are representative of areas outside of the zone or area ofinterest, the present invention may reduce the image data or informationto be processed by control 116 and may substantially reduce thepossibility that a false detection of a lane marker or the like willoccur. Lane departure warning system 110 may also process edges or imagedata within a further reduced image data set representative of atargeted portion or hot zone of the zone of interest to further identifyand confirm that the detected edge or edges are indicative of a lanemarker or the like or a vehicle or object that is significant to thelane departure warning system, such as discussed above with respect tolane change assist system 10.

By detecting edges of objects (such as lane markers, road edges,vehicles and the like) within the zone or area of interest (andoptionally adjusting the zone of interest for particular drivingconditions or situations), and by focusing on or concentrating on orprimarily processing the detected edges or image data which may beindicative of a lane marker or vehicle or significant object, whilesubstantially filtering out or substantially ignoring other edges orinformation or image data, the present invention substantially reducesthe possibility of falsely detecting lane markers or other significantvehicles or objects. Control 116 may be further operable to determine adistance between a detected object and the subject vehicle to furtherfilter out or substantially eliminate objects that are not within apredetermined range or threshold distance from the subject vehicle andwhich, thus, may be insignificant to the lane departure warning systemof the present invention, such as described above with respect to lanechange assist system 10.

Control 116 may also be operable to determine or estimate the distanceto the detected edge or object in response to the location of the pixelor pixels on the pixelated array which capture the detected edge orobject, such as in the manner also discussed above. The distance maythus be determined by determining the pixel location and accessing atable or data list or array to determine the distance associated withthe particular pixel.

Control 116 of lane departure warning system 110 may also be operable todetermine an intensity or brightness level associated with the detectededges and to substantially eliminate edges which do not significantlychange in brightness level or intensity level from one side of thedetected edge to the other. This is preferred, since thin branches onthe road and/or many other small articles or objects may not resolve,and thus may result in single edges that do not significantly change inbrightness or intensity (or color if a color system is used) acrosstheir detected edges. However, a sharp or significant change inbrightness or intensity would be expected at a detected edge of a lanemarker (since a lane marker is typically a white or yellow line segmentalong a dark or black or gray road surface) or an automotive body panelor bumper or other component or structure of a vehicle or the like.Accordingly, control 16 may substantially eliminate or substantiallyignore edges or objects which do not have a significant brightness orintensity change thereacross. By substantially eliminating suchinsignificant edges, control 16 may further significantly reduce thecomputational requirements or processing requirements, while alsosignificantly reducing the possibility of a false detection of a lanemarker or vehicle. It is further envisioned that lane departure warningsystem 110 may be capable of detecting lane markings and road edges andother vehicles and modifying the alert signal or process in response tothe type of marking, surrounding vehicles or the like and/or the vehiclemovement, such as disclosed in U.S. provisional application Ser. No.60/377,524, filed May 3, 2002, which is hereby incorporated herein byreference.

With reference to FIGS. 12 and 13, lane departure warning system 110 mayprovide a warning signal to a driver of vehicle 12 when the vehicle isabout to depart from its lane or road 113. The lane departure warningsystem 110 is operable in response to imaging sensor or camera 114positioned at a forward portion of the vehicle 12 (and may be positionedat a vehicle bumper area or at a windshield area, such as at an interiorrearview mirror or attachment thereto, without affecting the scope ofthe present invention) and having a field of view directed generallyforwardly with respect to the direction of travel of vehicle 12. Theimaging sensor 114 is operable to capture an image of a scene generallyforwardly (and preferably at least partially sidewardly) of the vehicle.The lane departure warning system includes image processing controls ordevices which may process the images captured to detect and identifyvarious objects within the image.

The imaging sensor useful with the present invention is preferably animaging array sensor, such as a CMOS sensor or a CCD sensor or the like,such as disclosed in commonly assigned U.S. Pat. Nos. 5,550,677;5,670,935; 5,796,094; and 6,097,023, and U.S. patent application, Ser.No. 09/441,341, filed Nov. 16, 1999, now U.S. Pat. No. 7,339,149, whichare hereby incorporated herein by reference. The imaging sensor may beimplemented and operated in connection with other vehicular systems aswell, or may be operable utilizing the principles of such othervehicular systems, such as a vehicle headlamp control system, such asthe type disclosed in U.S. Pat. No. 5,796,094, which is herebyincorporated herein by reference, a rain sensor, such as the typesdisclosed in commonly assigned U.S. Pat. Nos. 6,353,392; 6,313,454;and/or 6,320,176, which are hereby incorporated herein by reference, avehicle vision system, such as a forwardly directed vehicle visionsystem utilizing the principles disclosed in U.S. Pat. Nos. 5,550,677;5,670,935; and 6,201,642, and/or in U.S. patent application, Ser. No.09/199,907, filed Nov. 25, 1998, now U.S. Pat. No. 6,717,610, which arehereby incorporated herein by reference, a traffic sign recognitionsystem, a system for determining a distance to a leading vehicle orobject, such as using the principles disclosed in U.S. patentapplication, Ser. No. 09/372,915, filed Aug. 12, 1999, now U.S. Pat. No.6,396,397, which is hereby incorporated herein by reference, and/or thelike.

The lane departure warning system of the present invention is operableto provide a warning signal to a driver of the vehicle under at leastone of at least the following three conditions:

1) the vehicle is moving toward the edge of the road at a rapid speedindicating that the vehicle will actually depart from the pavement orshoulder;

2) the vehicle is moving into a lane with oncoming traffic present inthat lane; and/or

3) the vehicle is moving into a lane with traffic flowing in the samedirection and there is an adjacent vehicle in that lane (regardless ofturn signal use).

The lane departure warning system may be operable in response to one ormore of the detected conditions and may be further operable in responseto various vehicle characteristics or parameters, such as vehicle speed,a distance to the lane marker, shoulder, other vehicle, or any otherrelevant distance, road conditions, driving conditions, and/or the like.

With respect to the first condition (shown in FIG. 12), the lanedeparture warning system may be operable in response to a single forwardfacing imaging sensor or camera, to establish and track the road edge asdefined by two thresholds:

1) threshold 1: the edge 113 a of the road or pavement 113 (theintersection of the pavement 113 and the shoulder 113 b); and/or

2) threshold 2: the edge 113 c of the shoulder 113 b (the intersectionof the shoulder 113 b and the grass 113 d).

The lane departure warning system of the present invention may then beoperable to provide an audible warning, such as a rumble strip sound,when the vehicle is approaching threshold 1 and the vehicle is movingabove an established speed. The lane departure warning system may thenbe operable to provide a more urgent audible warning, such as an alarm,when the vehicle is approaching threshold 2 and is moving above theestablished speed. If the road does not have a shoulder, such as on somerural roads, there is only one threshold and this may correspond to athreshold 2 warning. The lane departure warning system may be operableto provide the warning signal or signals in response to the vehiclebeing a particular distance from the detected lane or road or shoulder.The distances to the threshold markings at which the lane departurewarning system initiates the warning signal or signals may varydepending on the speed of the vehicle, or other conditions surroundingthe vehicle, such as road conditions, driving conditions, or the like.

With respect to the second condition, the lane departure warning systemmay be operable in response to a single forward facing camera to monitorthe lane markings 113 e along the road surface and monitor the potentialpresence of oncoming traffic in an adjacent lane or lanes. Once thepresence of oncoming traffic has been established, the lane departurewarning system may issue an urgent audible warning if the vehicle beginsto cross the lane marking 113 e. Furthermore, if the vehicle has alreadybegun to cross into the oncoming traffic lane before oncoming traffic isdetected, the lane departure warning system may issue the urgent warningwhen oncoming traffic is detected.

Similar to the first condition, the lane departure warning system may beoperable in response to the second condition to initiate the warningsignal in response to different distances between the subject vehicleand the approaching vehicle, depending on the speed of one or bothvehicles, the driving conditions, the road conditions and/or the like.

With respect to the third condition (shown in FIG. 13), the lanedeparture warning system of the present invention may be operable inresponse to a single forward facing camera and at least one, andoptionally two, rearward and/or sideward facing cameras, to monitor thelane markings and the potential presence of adjacent traffic or vehicleor vehicles 112 in an adjacent lane 113 f, which may be traveling in thesame direction as the subject vehicle 12. Once the presence of adjacenttraffic has been established, the lane departure warning system mayissue an urgent audible warning to the driver of the vehicle if thesubject vehicle begins to cross the lane marking 113 e. Furthermore, ifthe subject vehicle has already begun to cross into the adjacent laneand then subsequently an adjacent vehicle is detected, the lanedeparture warning system may issue the urgent warning signal to thedriver of the vehicle.

Again, the lane departure warning system may be operable to initiate thewarning signal or signals in response to varying threshold parameters,which may vary depending on the speed of the subject vehicle, the speedof the other detected vehicle, the relative speed of the vehicles, thedriving conditions, the road conditions and/or the like. The lanedeparture warning system of the present invention may be operable todifferentiate between the different types of lane markings along roads,such as between solid and dashed lines and double lines.

Optionally, the lane departure warning system may be further operable todetect and recognize stop lights and/or stop signs and/or other road orstreet signs or markings, and to provide a warning signal to the driverof the vehicle in response to such detection. It is further envisionedthat the lane departure warning system of the present invention may beoperable to provide an alarm or broadcast an alarm or warning signal ona safety warning band when the forward facing camera detects a stoplight or stop sign and the system determines that the vehicle is notgoing to stop based on the vehicle's current speed and deceleration.This provides a signal or alarm to crossing drivers to warn them of anunsafe condition.

Optionally, the lane departure warning system of the present inventionmay be operable to determine the road conditions of the road on whichthe vehicle is traveling and/or the driving conditions surrounding thevehicle. The system may then provide the warning signal or signals inresponse to variable threshold values, such as different vehicle speedsor distances or the like. For example, wet or snowy roads would changethe distance and/or speed thresholds at which the lane departure warningsystem would provide the warning signal or signals. Also, becausedarkened or raining conditions may affect visibility of lane markers,road edges and other vehicles, the lane departure warning system of thepresent invention may be operable to provide a warning signal sooner orat a greater distance from the marker, edge or vehicle in such lowvisibility conditions. This provides the driver of the subject vehicle agreater amount of time to respond to the warning in such conditions.

The lane departure warning system of the present invention may beintegrated with a side object detection system (SOD). For example, thevehicle may be equipped with a camera or image-based side objectdetection system or a Doppler radar-based side object detection systemor other such systems (such as mounted on the side rearview mirrors orat the side of the vehicle) for detecting objects and/or vehicles at oneor both sides of the subject vehicle. The lane departure warningthreshold level or sensitivity at which the lane departure warningsystem generates a warning signal may then be adjustable in response todetection of a vehicle or object at a side of the subject vehicle anddetermination of the location and speed of the detected vehicle.Optionally, the signal generated may increase or decrease in intensityor volume in response to the position or speed of an object or vehicledetected by the side object detection system. For example, the thresholdlevel may take into account the approach speed of the other vehicle tothe subject vehicle, and may provide a louder or brighter warning to thedriver of the subject vehicle if the approach speed is above aparticular threshold level or threshold levels.

The lane departure warning system may be provided with a multi-featureor multi-function forward facing imaging system. The imaging system maycombine two or more functions, such as an intelligent headlampcontroller (such as the type disclosed in U.S. Pat. Nos. 5,796,094 and6,097,023, and U.S. patent application, Ser. No. 09/441,341, filed Nov.16, 1999, now U.S. Pat. No. 7,339,149, which are hereby incorporatedherein by reference), an image-based smart wiper controller, a rainsensor (such as the types disclosed in commonly assigned U.S. Pat. Nos.6,353,392; 6,313,454; and/or 6,320,176, which are hereby incorporatedherein by reference), an image-based climate control blower controller,an image-based or image-derived or partially derived adaptivecruise-control system (where the imaging may be primary or secondary toa forward facing Doppler radar), and/or other vision systems (such as aforwardly directed vehicle vision system utilizing the principlesdisclosed in U.S. Pat. Nos. 5,550,677; 5,670,935; and 6,201,642, and/orin U.S. patent application, Ser. No. 09/199,907, filed Nov. 25, 1998,now U.S. Pat. No. 6,717,610, which are all hereby incorporated herein byreference), a traffic sign recognition system, a system for determininga distance to a leading vehicle or object (such as using the principlesdisclosed in U.S. patent application, Ser. No. 09/372,915, filed Aug.12, 1999, now U.S. Pat. No. 6,396,397, which is hereby incorporatedherein by reference), and/or the like.

For example, an embodiment of the lane departure warning system of thepresent invention may be incorporated with or integrated with anintelligent headlamp control system (such as described in U.S. Pat. Nos.5,796,094 and 6,097,023, and U.S. patent application, Ser. No.09/441,341, filed Nov. 16, 1999, now U.S. Pat. No. 7,339,149, which arehereby incorporated herein by reference) having an imaging array sensorfeeding a signal or image to a microcontroller (which may comprise amicroprocessor or microcomputer), which is operable to adjust a state ofthe headlamps in response to a captured image of the scene forwardly ofthe vehicle. The image captured by the imaging sensor may be analyzedfor light sources of interest for the headlamp control, and also forlane markings, road edges, and other objects of interest (such as roadsigns, stop signs, stop lights and/or the like) for the lane departurewarning system. Optionally, the lane departure warning system may beintegrated with or tied to an existing headlamp control of the vehicle.

The lane departure warning system of the present invention thus may beimplemented as part of one or more other imaging-based systems, and thusmay share components, hardware and/or software with the other systems toreduce the incremental costs associated with the lane departure warningsystem and with the other systems as well. Accordingly, multiple systemsmay be provided by an automotive supplier as part of a common platformor module for each vehicle of a particular vehicle line or model. Thevehicle manufacturer may then choose to activate or enable one or moreof the systems of the module, depending on which options are selected ona particular vehicle. Therefore, the addition or selection of the lanedeparture warning system, or of one or more other imaging-based systems,is associated with an incremental addition of hardware and/or software,and thus of associated costs, in order to install and enable the systemon a particular vehicle. The imaging array sensor or sensors of themodule may then be interrogated by an appropriate processor or softwareto extract the light sources or objects of interest or pixels ofinterest for each respective system of the common or unitary module. Forexample, an image captured by the imaging array sensor or camera may beprocessed or analyzed one way for a headlamp control system, and thenprocessed or analyzed another way for the lane departure warning systemor for any other enabled functions or systems of the common module. Thesoftware may further include common blocks or functions or macros tofurther enhance the sharing of software between the systems.

Accordingly, a unitary module may be provided to a vehicle assemblyplant and may include multiple features, systems or functions, such thatthe desired features, systems or functions may be enabled for aparticular vehicle, with minimal additional software or components orhardware being associated with the features, systems or functions thatare enabled. The anchor system of the common or unitary module orplatform may be an intelligent headlamp controller, with the additionalsystems, such as the lane departure warning system of the presentinvention, being added to or integrated with the anchor system.

The lane departure warning system and any other associated imaging-basedsystems may be included as part of an interior rearview mirror assemblyor as part of an electronic windshield module and/or accessory moduleassembly, such as disclosed in commonly assigned U.S. Pat. Nos.6,243,003; 6,278,377; and 6,433,676; U.S. patent applications, Ser. No.10/054,633, filed Jan. 22, 2002, now U.S. Pat. No. 7,195,381; and Ser.No. 09/792,002, filed Feb. 26, 2001, now U.S. Pat. No. 6,690,268; Ser.No. 09/585,379, filed Jun. 1, 2000; Ser. No. 09/466,010, filed Dec. 17,1999, now U.S. Pat. No. 6,420,975; and Ser. No. 10/355,454, filed Jan.31, 2003, now U.S. Pat. No. 6,824,281, which are all hereby incorporatedherein by reference.

Therefore, the lane departure warning system of the present inventionprovides a warning signal or signals to a driver of a vehicle based onthe detection of various objects, vehicles and conditions surroundingthe vehicle. The lane departure warning system of the present inventionis thus less likely to provide a warning signal to a driver of thevehicle when the driver intends to maneuver the vehicle in that manner,and thus where such a warning signal is not needed or wanted. The lanedeparture warning system of the present invention thus avoids annoying,unnecessary warnings, and thus provides improved responses by the driverof the vehicle, since the driver is less likely to ignore the signalprovided by the lane departure warning system. The lane departurewarning system of the present invention may be implemented with orintegrated with one or more other imaging-based systems to reduce theincremental components, hardware, software and costs associated with theimplementation of the lane departure warning system.

Optionally, the object detection system or imaging system of the presentinvention may be operable in conjunction with a passive steering system210 (FIG. 1), which is operable to adjust or bias the steering directionof the vehicle toward a center region of a lane in response to detectionof the lane markers or road edges or the like by the imaging system.Passive steering system 210 may be in communication with or connected toa steering system of the vehicle and may adjust or bias the steeringdirection of the vehicle slightly if the lane departure warning systemdetects a slow drifting of the vehicle out of its lane and may befurther operable in response to a detected road curvature ahead of thevehicle. The passive steering system 210 may steer the vehicle back intoits lane or keep the vehicle in its lane when such a drifting conditionis detected. The passive steering system may function to bias thesteering of the vehicle toward the center of the occupied lane, but maybe easily overcome by manual steering of the vehicle by the driver, suchthat the driver at all times maintains ultimate control over thesteering of the vehicle. The passive steering system thus may functionas a lane detent which maintains the vehicle in its lane, but may beeasily overcome or disabled if the steering wheel is manually turned orif a turn signal is activated or the like.

The passive steering assist system of the present invention thus mayreduce driver fatigue from driving a vehicle under conditions whichrequire constant driver steering input or adjustment, such as in windyconditions and the like. The passive steering assist system thus mayreduce lane drift from side to side within a lane. Also, overall safetymay be improved by the reduction in undesired lane maneuvers. Althoughdescribed as being responsive to the imaging system of the presentinvention, the passive steering system of the present invention may beresponsive to other types of lane departure warning systems or othertypes of vision or imaging systems, without affecting the scope of thepresent invention.

Optionally, the object detection system or imaging system of the presentinvention may be operable in connection with an adaptive speed controlsystem 310 (FIG. 1), which may adjust the cruise control setting orspeed of the vehicle in response to road or traffic conditions detectedby the imaging system. For example, adaptive speed control system 310may reduce the set speed of the vehicle in response to the imagingsystem (or other forward facing vision system) detecting a curve in theroad ahead of the vehicle. The vehicle speed may be reduced to anappropriate speed for traveling around the curve without the driverhaving to manually deactivate the cruise control. The adaptive speedcontrol may then resume the initial speed setting after the vehicle isthrough the turn or curve and is again traveling along a generallystraight section of road. Adaptive speed control 310 may also reduce thespeed of the vehicle or even deactivate the cruise control setting inresponse to a detection by the lane departure warning system or othervision system of taillights or headlamps of another vehicle detected infront of the subject vehicle and within a threshold distance of thesubject vehicle or approaching the subject vehicle at a speed greaterthan a threshold approach speed, or in response to detection of otherobjects or conditions which may indicate that the speed of the vehicleshould be reduced.

Additionally, because the imaging system, such as a forward facing lanedeparture warning system, may track the lane curvature, the system mayalso be able to determine if a vehicle which appears in front of thesubject vehicle is actually in the same lane as the subject vehicle orif it is in an adjacent lane which is curving with the section of road.The imaging system and adaptive speed control system may then establishif the vehicle speed should be reduced in response to the road curvatureand the presence of another vehicle at the curve. Although described asbeing responsive to the imaging system or lane departure warning systemof the present invention, the adaptive speed control system of thepresent invention may be responsive to other types of lane departurewarning systems or other types of vision or imaging systems,particularly other types of forward facing imaging systems, withoutaffecting the scope of the present invention.

It is further envisioned that the imaging system, which may comprise anobject detection system, a lane change assist system, a side objectdetection system, a lane departure warning system or other forwardfacing vision system, a rear vision system or park aid or panoramic viewsystem, a passive steering system, an adaptive cruise control system orthe like, may be in communication with a security monitoring system. Thevision or image data from the imaging system may be transmitted to aremote device, such as the vehicle owner's computer monitor or otherpersonal display system remote from the vehicle, so that the owner ofthe vehicle or other person may view the status of the area surroundingthe vehicle when the owner or other person is not in the vehicle. Also,the vision or image data may be provided to or made available to thelocal police authorities or the like in the event of a theft of thevehicle or of an accident involving the vehicle or of the vehicle beingotherwise inoperable (such as when the motorist is stranded). The policeor emergency services or the like may use the vision or image data todetermine the vehicle location and possibly the condition of the vehicleand/or the driver and/or the passengers. It is further envisioned thatthe vision or image data may be used in conjunction with the globalpositioning system (GPS) of the vehicle to precisely locate or pinpointthe vehicle location. The vision or image data may be transmitted to theremote device or to the emergency services or the like via varioustransmission devices or systems, such as utilizing Bluetooth technologyor the like, without affecting the scope of the present invention.

Therefore, the present invention provides a vision or imaging system orobject detection system which is operable to detect and process edgeswithin a captured image or images to determine if the edges areindicative of a significant vehicle or object or the like at or near orapproaching the subject vehicle. The imaging system may primarilyprocess a reduced image data set representative of a zone of interest ofthe exterior scene and may process edges that are detected which arerepresentative of an object within the zone of interest of the capturedimage. The imaging system may adjust the reduced data set or zone ofinterest in response to various conditions or characteristics orcriteria. The imaging system may comprise an object detection system ora lane change assist system operable to detect objects or other vehiclesat one or both sides of the subject vehicle. The object detection systemmay determine the distance to the detected object or edge and may adjustthreshold criterion in response to the determined or estimated orcalculated distance.

Optionally, the imaging system may comprise a forward facing lanedeparture warning system which may be operable to detect lane markers orthe like and/or vehicles in front of the subject vehicle and to providean alert signal to the driver of the vehicle that the vehicle is leavingits lane. The lane departure warning system may primarily process edgesdetected within a zone of interest within the captured image. The lanedeparture warning system may determine a distance to the detected edgeor object and may vary or adjust threshold criterion in response to thedetermined or estimated or calculated distance.

The forward facing imaging system may be in communication with the lanechange assist system of the vehicle and/or may be in communication withother systems of the vehicle, such as a side object detection system, apassive steering system or an adaptive speed control system or the like.The imaging system may communicate to the lane change assist system thatthe vehicle is approaching a curve in the road or that another vehicleis being approached and passed by the subject vehicle to assist inprocessing the image data captured by the sensor or camera of the lanechange assist system. Optionally, a passive steering system may adjust asteering direction of the vehicle in response to the imaging system, oran adaptive speed control system may adjust a cruise control setting ofthe vehicle in response to the imaging system. Optionally, an output ofthe imaging system may be provided to or communicated to a remotereceiving and display system to provide image data for viewing at alocation remote from the subject vehicle.

Changes and modifications in the specifically described embodiments maybe carried our without departing from the principles of the presentinvention, which is intended to limited only by the scope of theappended claims, as interpreted according to the principles of patentlaw.

1. A vision system for a vehicle, said vision system comprising: animaging sensor disposed at a vehicle equipped with said vision system,wherein said imaging sensor comprises a plurality of photo-sensingpixels, and wherein said imaging sensor has a field of view exteriorlyof the equipped vehicle, and wherein said imaging sensor is operable tocapture an image data set representative of a scene occurring exteriorlyof the equipped vehicle and in the exterior field of view of saidimaging sensor; a processor for processing said captured image data setvia an edge detection algorithm; wherein said edge detection algorithmis applied to a reduced image data set of said captured image data setto detect edges of objects present exteriorly of the equipped vehicleand within a target zone within the exterior field of view of saidimaging sensor; wherein said reduced data set is processed more thanother image data of said captured image data set in order to detectobjects present exteriorly of the equipped vehicle and within saidtarget zone; and wherein said target zone encompasses a geographic areaof the exterior scene where an object of interest to the driver of theequipped vehicle is realistically expected to be present.
 2. The visionsystem of claim 1, wherein said other image data is representative ofother geographic areas of the exterior scene where an object of interestis unrealistically expected to be present or cannot be present.
 3. Thevision system of claim 1, wherein said target zone is selected inaccordance with an adjustment input.
 4. The vision system of claim 3,wherein said adjustment input comprises at least one of (i) an outputfrom an ambient light sensor, (ii) a headlamp control, (iii) a manualcontrol, (iv) a daytime driving condition for the equipped vehicle, (v)a night-time driving condition for the equipped vehicle, (vi) theequipped vehicle traveling through or along a curved section of road,(vii) an output from a separate forward facing imaging system, (viii) anexternal lighting condition and (ix) a mathematical adjustment of theheight of the captured image such that the geometry of the target zoneis adjusted.
 5. The vision system of claim 1, wherein said target zoneis selected responsive, at least in part, to at least one of (i) anambient light sensor, (ii) a headlamp control and (iii) a manualcontrol.
 6. The vision system of claim 1, wherein said imaging sensorhas its exterior field of view at least partially sidewardly and atleast partially rearwardly relative to the equipped vehicle.
 7. Thevision system of claim 6, wherein said vision system comprises a lanechange assist system.
 8. The vision system of claim 1, wherein saidimaging sensor comprises a forward facing imaging sensor and is operableto capture at least one of oncoming traffic information, leading trafficinformation and lane marking information.
 9. The vision system of claim1, wherein said processor is operable to provide a warning indication toa driver of the equipped vehicle in response to a condition detected bysaid vision system.
 10. The vision system of claim 9, wherein saidprocessor provides a first warning in response to a detection that theequipped vehicle is on course to leave a lane of a road traveled by theequipped vehicle and travel onto a shoulder of the road traveled by theequipped vehicle and a second warning in response to a detection thatthe equipped vehicle is on course to leave the shoulder of the roadtraveled by the equipped vehicle.
 11. The vision system of claim 1,wherein said vision system is operable to adjust a steering direction ofthe equipped vehicle in response to a detection by said vision system ofthe equipped vehicle drifting or leaving its occupied lane.
 12. Thevision system of claim 1, wherein said vision system is operable toadjust a cruise control setting of the equipped vehicle in response toroad or traffic conditions detected by said vision system.
 13. Thevision system of claim 1, wherein said vision system is selectivelyoperable to provide image data to a remote device that is remote fromthe equipped vehicle, and wherein said vision system provides said imagedata to indicate a location and/or condition of the equipped vehicle.14. The vision system of claim 13, wherein said remote device comprisesat least one of a personal display system, a security display system andan emergency display system.
 15. The vision system of claim 1, whereinsaid target zone is adjusted responsive to a daytime or nighttimedriving condition for the equipped vehicle.
 16. The vision system ofclaim 1, wherein said target zone is adjusted in response to a distanceto a detected object.
 17. The vision system of claim 1, wherein adistance to a portion of at least one detected object is approximated.18. The vision system of claim 17, wherein said pixel location isdetermined relative to a target pixel which is directed generally at thehorizon and along the direction of travel of the equipped vehicle. 19.The vision system of claim 17, wherein said distance is approximated inresponse to at least one of a pixel size, a pixel resolution and a fieldof view of said imaging sensor.
 20. The vision system of claim 1,wherein a distance to a portion of at least one detected object isapproximated in response to a pixel location of the portion in saidcaptured image.
 21. The vision system of claim 1, wherein said processoris operable to process horizontal detected edges and substantially limitprocessing of vertical detected edges.
 22. The vision system of claim 1,wherein said processor is operable to process horizontal detected edgesand substantially limit processing of vertical detected edges and reducethe amount of data to be processed downstream.
 23. The vision system ofclaim 1, wherein said processor is operable to process detected edgeswhich have a concentration of edges in a second reduced image data setwhich is representative of a particular reduced area or zone of saidtarget zone of said captured image.
 24. The vision system of claim 1,wherein said processor is operable to substantially limit processing ofdetected edges having an intensity that is less than a thresholdintensity.
 25. The vision system of claim 1, wherein said processor isoperable to determine whether detected edges constitute a portion of avehicle.
 26. The vision system of claim 25, wherein said processor isoperable to determine that detected edges may constitute a portion of avehicle in response to a determination that said detected edges areassociated with an ellipse or partial ellipse, said ellipse or partialellipse being indicative of a vehicle tire.
 27. The vision system ofclaim 1, wherein said processor is operable to determine whetherdetected edges constitute a portion of a vehicle in an adjacent lane.28. The vision system of claim 1, wherein said processor is operable totrack at least one detected edge between subsequent frames captured bysaid imaging sensor.
 29. The vision system of claim 1, wherein saidprocessor is operable to primarily process detected edges orsubstantially limit processing of detected edges in response to at leastone of a size, location, intensity and distance of said detected edgesrelative to the equipped vehicle.
 30. The vision system of claim 1,wherein said processor is operable to identify lane or road markings inimages captured by said imaging sensor.
 31. The vision system of claim1, wherein said processor is operable to identify lane or road markingsin images captured by said imaging sensor to determine road curvature ofthe road section that the equipped vehicle is traveling along.
 32. Thevision system of claim 31, wherein said processor is operable to adjustsaid target zone in response to an identification of a curve in the roadsection.
 33. A vision system for a vehicle, said vision systemcomprising: an imaging sensor disposed at a vehicle equipped with saidvision system, wherein said imaging sensor comprises a plurality ofphoto-sensing pixels, and wherein said imaging sensor has a field ofview exteriorly of the equipped vehicle, and wherein said imaging sensoris operable to capture an image data set representative of a sceneoccurring exteriorly of the equipped vehicle and in the exterior fieldof view of said imaging sensor; wherein said imaging sensor comprises aCMOS sensor; a processor for processing said captured image data set viaan edge detection algorithm; wherein said edge detection algorithm isapplied to a reduced image data set of said captured image data set todetect edges of objects present exteriorly of the equipped vehicle andwithin a target zone within the exterior field of view of said imagingsensor; wherein said reduced data set is processed more than other imagedata of said captured image data set in order to detect objects presentexteriorly of the equipped vehicle and within said target zone; whereinsaid target zone encompasses a geographic area of the exterior scenewhere an object of interest to the driver of the equipped vehicle isrealistically expected to be present; and wherein said imaging sensorcomprises a forward facing imaging sensor and is operable to capture atleast one of oncoming traffic information, leading traffic informationand lane marking information.
 34. The vision system of claim 33, whereinsaid target zone is selected in accordance with an adjustment input, andwherein said adjustment input comprises at least one of (i) an outputfrom an ambient light sensor, (ii) a headlamp control, (iii) a manualcontrol, (iv) a daytime driving condition for the equipped vehicle, (v)a night-time driving condition for the equipped vehicle, (vi) theequipped vehicle traveling through or along a curved section of road,(vii) an output from a separate forward facing imaging system, (viii) anexternal lighting condition and (ix) a mathematical adjustment of theheight of the captured image such that the geometry of the target zoneis adjusted.
 35. The vision system of claim 33, wherein said processoris operable to provide a warning indication to a driver of the equippedvehicle in response to at least two conditions detected by said visionsystem, and wherein said processor provides a first warning in responseto a detection that the equipped vehicle is on course to leave a lane ofa road traveled by the equipped vehicle and travel onto a shoulder ofthe road traveled by the equipped vehicle and a second warning inresponse to a detection that the equipped vehicle is on course to leavethe shoulder of the road traveled by the equipped vehicle.
 36. Thevision system of claim 33, wherein said vision system is operable toadjust a steering direction of the equipped vehicle in response to adetection by said vision system of the equipped vehicle drifting orleaving its occupied lane.
 37. The vision system of claim 33, whereinsaid target zone is adjusted responsive to a daytime or nighttimedriving condition for the equipped vehicle.
 38. The vision system ofclaim 33, wherein said processor is operable to identify lane or roadmarkings in images captured by said imaging sensor.
 39. The visionsystem of claim 33, wherein said processor is operable to identify laneor road markings in images captured by said imaging sensor to determineroad curvature of the road section that the equipped vehicle istraveling along.
 40. The vision system of claim 39, wherein saidprocessor is operable to adjust said target zone in response to anidentification of a curve in the road section.
 41. The vision system ofclaim 33, wherein at least one of (i) said processor is operable toprocess horizontal detected edges and substantially limit processing ofvertical detected edges, (ii) said processor is operable to processhorizontal detected edges and substantially limit processing of verticaldetected edges and reduce the amount of data to be processed downstream,(iii) said processor is operable to process detected edges which have aconcentration of edges in a second reduced image data set which isrepresentative of a particular reduced area or zone of said target zoneof said captured image, (iv) said processor is operable to substantiallylimit processing of detected edges having an intensity that is less thana threshold intensity, (v) said processor is operable to determine thatdetected edges may constitute a portion of a vehicle in response to adetermination that said detected edges are associated with an ellipse orpartial ellipse, said ellipse or partial ellipse being indicative of avehicle tire, (vi) said processor is operable to track at least onedetected edge between subsequent frames captured by said imaging sensor,and (vii) said processor is operable to primarily process detected edgesor substantially limit processing of detected edges in response to atleast one of a size, location, intensity and distance of said detectededges relative to the equipped vehicle.
 42. The vision system of claim33, wherein said other image data is representative of other geographicareas of the exterior scene where an object of interest isunrealistically expected to be present or cannot be present.
 43. Avision system for a vehicle, said vision system comprising: an imagingsensor disposed at a side of a vehicle equipped with said vision system,wherein said imaging sensor comprises a plurality of photo-sensingpixels, and wherein said imaging sensor has a field of view exteriorlyof the equipped vehicle, and wherein said imaging sensor is operable tocapture an image data set representative of a scene occurring exteriorlyof the equipped vehicle and in the exterior field of view of saidimaging sensor; a processor for processing said captured image data setvia an edge detection algorithm; wherein said edge detection algorithmis applied to a reduced image data set of said captured image data setto detect edges of objects present exteriorly of the equipped vehicleand within a target zone within the exterior field of view of saidimaging sensor; wherein said reduced data set is processed more thanother image data of said captured image data set in order to detectobjects present exteriorly of the equipped vehicle and within saidtarget zone; wherein said target zone encompasses a geographic area ofthe exterior scene where an object of interest to the driver of theequipped vehicle is realistically expected to be present; and whereinsaid imaging sensor has its exterior field of view at least partiallysidewardly and at least partially rearwardly relative to the equippedvehicle.
 44. The vision system of claim 43, wherein said vision systemcomprises a lane change assist system.
 45. The vision system of claim43, wherein said imaging sensor is accommodated in a side rearviewmirror at the side of the equipped vehicle.
 46. The vision system ofclaim 43, wherein said target zone is selected in accordance with anadjustment input, and wherein said adjustment input comprises at leastone of (i) an output from an ambient light sensor, (ii) a headlampcontrol, (iii) a manual control, (iv) a daytime driving condition forthe equipped vehicle, (v) a night-time driving condition for theequipped vehicle, (vi) the equipped vehicle traveling through or along acurved section of road, (vii) an output from a separate forward facingimaging system, (viii) an external lighting condition and (ix) amathematical adjustment of the height of the captured image such thatthe geometry of the target zone is adjusted.
 47. The vision system ofclaim 43, wherein said processor is operable to provide a warningindication to a driver of the equipped vehicle.
 48. The vision system ofclaim 43, wherein said processor is operable to provide a warningindication to a driver of the equipped vehicle in response to at leasttwo conditions detected by said vision system, and wherein saidprocessor provides a first warning in response to a detection that theequipped vehicle is on course to leave a lane of a road traveled by theequipped vehicle and travel onto a shoulder of the road traveled by theequipped vehicle and a second warning in response to a detection thatthe equipped vehicle is on course to leave the shoulder of the roadtraveled by the equipped vehicle.
 49. The vision system of claim 43,wherein said vision system is operable to adjust a steering direction ofthe equipped vehicle in response to a detection by said vision system ofthe equipped vehicle drifting or leaving its occupied lane.
 50. Thevision system of claim 43, wherein said target zone is adjustedresponsive to a daytime or nighttime driving condition for the equippedvehicle.
 51. A vision system for a vehicle, said vision systemcomprising: an imaging sensor disposed at a vehicle equipped with saidvision system, wherein said imaging sensor comprises a plurality ofphoto-sensing pixels, and wherein said imaging sensor has a field ofview exteriorly of the equipped vehicle, and wherein said imaging sensoris operable to capture an image data set representative of a sceneoccurring exteriorly of the equipped vehicle and in the exterior fieldof view of said imaging sensor; a processor for processing said capturedimage data set via an edge detection algorithm; wherein said edgedetection algorithm is applied to a reduced image data set of saidcaptured image data set to detect edges of objects present exteriorly ofthe equipped vehicle and within a target zone within the exterior fieldof view of said imaging sensor; wherein said reduced data set isprocessed more than other image data of said captured image data set inorder to detect objects present exteriorly of the equipped vehicle andwithin said target zone; wherein said target zone encompasses ageographic area of the exterior scene where an object of interest to thedriver of the equipped vehicle is realistically expected to be present;and wherein said imaging sensor comprises a forward facing imagingsensor and is operable to capture oncoming traffic information, leadingtraffic information and lane marking information.
 52. The vision systemof claim 51, wherein said other image data is representative of othergeographic areas of the exterior scene where an object of interest isunrealistically expected to be present or cannot be present.
 53. Thevision system of claim 51, wherein said processor is operable todetermine whether detected edges constitute a portion of a vehicle. 54.The vision system of claim 51, wherein a distance to a portion of atleast one detected object is approximated.
 55. The vision system ofclaim 51, wherein a distance to a portion of at least one detectedobject is approximated in response to a pixel location of the portion insaid captured image.
 56. The vision system of claim 51, wherein saidprocessor is operable to provide a warning indication to a driver of theequipped vehicle in response to a condition detected by said visionsystem.
 57. A vision system for a vehicle, said vision systemcomprising: an imaging sensor disposed at a vehicle equipped with saidvision system, wherein said imaging sensor comprises a plurality ofphoto-sensing pixels, and wherein said imaging sensor has a field ofview exteriorly of the equipped vehicle, and wherein said imaging sensoris operable to capture an image data set representative of a sceneoccurring exteriorly of the equipped vehicle and in the exterior fieldof view of said imaging sensor; wherein said imaging sensor comprises aCMOS sensor; a processor for processing said captured image data set viaan edge detection algorithm; wherein said edge detection algorithm isapplied to a reduced image data set of said captured image data set todetect edges of objects present exteriorly of the equipped vehicle andwithin a target zone within the exterior field of view of said imagingsensor; wherein said reduced data set is processed more than other imagedata of said captured image data set in order to detect objects presentexteriorly of the equipped vehicle and within said target zone; whereinsaid target zone encompasses a geographic area of the exterior scenewhere an object of interest to the driver of the equipped vehicle isrealistically expected to be present; and wherein said imaging sensorcomprises a forward facing imaging sensor and wherein said processor isoperable to identify lane or road markings in images captured by saidimaging sensor.
 58. The vision system of claim 57, wherein saidprocessor is operable to identify lane or road markings in imagescaptured by said imaging sensor to determine road curvature of the roadsection that the equipped vehicle is traveling along.
 59. The visionsystem of claim 58, wherein said processor is operable to adjust saidtarget zone in response to an identification of a curve in the roadsection.
 60. The vision system of claim 57, wherein said target zone isselected in accordance with an adjustment input, and wherein saidadjustment input comprises at least one of (i) an output from an ambientlight sensor, (ii) a headlamp control, (iii) a manual control, (iv) adaytime driving condition for the equipped vehicle, (v) a night-timedriving condition for the equipped vehicle, (vi) the equipped vehicletraveling through or along a curved section of road, (vii) an outputfrom a separate forward facing imaging system, (viii) an externallighting condition and (ix) a mathematical adjustment of the height ofthe captured image such that the geometry of the target zone isadjusted.
 61. The vision system of claim 57, wherein said other imagedata is representative of other geographic areas of the exterior scenewhere an object of interest is unrealistically expected to be present orcannot be present.
 62. The vision system of claim 57, wherein saidprocessor is operable to determine whether detected edges constitute aportion of a vehicle.
 63. The vision system of claim 57, wherein adistance to a portion of at least one detected object is approximated inresponse to a pixel location of the portion in said captured image. 64.The vision system of claim 57, wherein said processor is operable toprovide a warning indication to a driver of the equipped vehicle inresponse to a condition detected by said vision system.